Welding system



Aug. 2, 1949.

J. w. DAWSON WELDING SYSTEM Filed March 15, 1946 SULEIO/D M l E/VTO/T" JOHN W 0191750 Patented Aug. 2, 1949 UNITED STATES PATENT OFFICE WELDING SYSTEM John W. Dawson, West Newton, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application March 13, 1946, Serial No. 654,048

.6 Claims. 1

This invention relates to a system and method for welding by means of electric current.

An object of this invention is to devise a machine and method for producing smooth uniform welds.

Another object is to heat the portion of a body to be welded to a very high temperature without producing any substantial flowing of the metal.

A further object is to concentrate the heat pro duced in a resistance-welding process in the portion of the body to be welded.

Another object is to provide a method for accomplishing preliminary heating of the portion of a body to be later welded by the resistancewelding method, whereby the welding itself may be performed more efficiently.

The foregoing and other objects of the invention will be best understood from the followin description of an exemplification thereof, reference being had to the accompanying drawing wherein the figure is a cross-sectional view of an apparatus for carrying out the invention, together with a diagrammatic circuit of the systern.

In the drawing, two metal bodies I and 2 which are shown in the form of tubes or pipes are to be welded to each other along their adjacent edges so as to form a continuous tube or pipe. The pipes are held spaced apart so as to provide an annular gap 4, in which an arc is to be established. A rod 3 of magnetic material is inserted inside the pipes I and 2 so as to extend past the gap 4 to a point substantially above said gap.

Surrounding the pipes I and 2, respectively, is a pair of magnetic shells 5-5. Each of these shells is provided with aligned openings 6 and I through which the pipes may be inserted. In the outer annular space provided in each of the shells 5, an annular coil 8 is placed for the purpose of setting up a magnetic flux in each of the shells 5. If desired a refractory washer 8' may be placed at one end of each coil 8 so as to shield and protect said coil against the heat generated by the arc in the gap 4. The terminals of each coil 8 are provided with leads 9 passing through insulating bushings to the exterior of the shells 5. The leads 9 are arranged to connect the coils 8 in series with each other and with a source of magnetizing current, such as a direct current source Ill.

The edges of the openings I in the shells 5 provide adjacent annular pole pieces II-I I. If desired the faces of the pole pieces II may likewise be protected from the heat of the are by coating said faces with refractory material. The coils 8 are selected of such polarity as to make the adjacent pole pieces IIII of the same polarity. For example, the adjacent poles IIII may be made south poles. The edges of the openings 6 provide the opposite poles I2 which, in the example given above, will be north poles. Upon energizing the coils 8 as described, the rod 3 Will have a localized south pole produced adjacent each of the annular poles I2, and a localized central north pole adjacent the annular pole pieces II. Under these conditions a substantial amount of magnetic flux will pass radially throughout substantially the entire gap 4.

In order to hold the pipes I and 2 in the position as described, the lower pipe 2 may be securely held in a clamp I3 which is rigidly held in place by stationary base members I8-I8. The upper pipe I may be held in a clamping member I4 supported by movable members I9I9, which are slidably mounted on stationary base members .2Il--20 so as to be movable in the directions indicated by the arrows thereon. The movable members I9-I9 are actuated so as to move pipe I in the vertical direction by a means to be described hereinafter. The movable members I9 are adapted to hold the pipes I and 2 separated by a predetermined amount, and to move the lower end of the pipe I into intimate engagement with the upper end of the pipe 2.

The pipes I and 2 have electrically connected thereto conductors I5 and I6 which are connected respectively to the two terminals of a suitable source of arc current II. The source I! may supply current of any suitable nature, which may be in the form of direct current or alternating current, or any specialized current form particularly adapted for the purpose for which it is to be used.

In order to actuate the movable members I9I9, so as to move pipe I into engagement with pipe 2, a pneumatically-operated actuating means is provided. This means includes an annular cylinder 2| rigidly fixed to base members 20-40 and adapted to be supplied with cornpressed air from an air inlet pipe 22 through an inlet valve 23. Cylinder 2| contains an annular piston having two diametrically opposite rods 24 and 25 attached thereto. Rods 24 and 25 are attached, at their opposite ends, to movable members I9I9. It will therefore be apparent that, when compressed air is supplied to cylinder .2I, rods 24 and 25 will be moved downwardly, thereby forcing movable members I9I9 and pipe I downwardly, also. Inlet valve 23 is adapted to be actuated by a solenoid 26 through a mechanical connection 21. Solenoid 526 is energized from any suitable source 30 through leads 28 and switch 29.

A timing unit 3| is provided, having control terminals 32, power input terminals 33, and power outputterminals 34. Thisunit, .as schematically indicated, is of the electronic type and is adapted, in response to a control Voltage, to act as a switch whereby current is supplied from a source to a load for a predetermined time interval. Such timing units are well-known to those skilled in the art, Control terminals 32 of the unit 3i are connected to source 3 through switch 29. Power input terminals 33 are connected to a suitable alternating-current source 35. One of the power output terminals 34 is connected, by means oi lead to pipe l, while the other output terminal 3 3 is connected, by lead 3?, to pipe2.

A switch 38 may be connected so as to control the arc current source IT. The switches 38 and 29 may be so interlocked that, a predetermined time interval afterswitch 38 is closed to energize source H,switch 29 will also be closed. If

desired, theseswitches may further be arranged so that when switch 29 closes, switch 38will. open.

Source l may be continuously energized. When'switch 38- is closed to energize source H, anarc isstruck in the gap. 4 in any suitable manner. For example, the arc may be struck by moving thepipe I. into. engagement with the pipe 2, and then. separating the edges of said pipes inorder to strike thearc. An arc in the sense as usedin the specification and claims is an electrical spacedischarge which occurs between two separated surfaces, of sufficient intensity to produce substantial heating of. the surface between which. the discharge passes. Thecurrent of the are flowslongitudinally through the gap 4 while i themagnetic field described passes radially through said gap. The reaction between this current and flux produces a force at right angles to: the current and flux. around the annular gap 4. Thisreaction, therefore, produces a dispers-ion. of the arcthroughout. th gap 4.. The magnetic. field moves the are at high speed around the gap so that; the entire adjacent end portions of pipes l and 2 are heated. to a. high temperature.

The. time elapsing between. the closing of Switches 38 and 29 is made such that. the arc heats the-end portions of pipes. I, and 2 to a high temperature, but onewhich is below the-drip point of the metal of pipes l and 2-,.so that the metal of the pi es. does. not tend, to drip or flow- It willbe recalled that the arc current source I! is energized when switch 38 is closed and is deenergized when switch. 29 closes, so that the length. of time the arc current is applied to the pipes will dependon the time elapsing between closing of switches38 and 29- and may be made such that the above-described temperature of the end portions of pipes l and .2 is reached at the time the arc current is shut 01f. Whenswitch 29 closes, solenoid 26 is energized from source 33 to open inletv valve 23, admittingair. under pressure to cylinder 2|. This causes the piston within. said cylinder to. be driven downwardly, thus forcing. movable members l9| 9' and pipe I downwardly alsduntilthe adjacent ends ofpipes ly and 2,,which have beenraised to a. high tempcrature by the heat of thearc, are pushed together. Since the control terminals. 32v ofv unit 3l'are connected to the source through switch 29, when this switch closes a control voltage will be applied to unit 31. In response to this control voltage, unit 3| will cause alternating current to be supplied from source 35 to pipes l and 2 for a predetermined time interval (i. e., for a predetermined number of cycles of source 35).

While the alternating. current. of high value is being applied to pipes I and 2 from source 35 through unit 3|, pipes l and 2 are in tight engagement with each other, so that the end surfaces thereof are heated to welding temperature by the current passing therethrough and the said surfaces are fused or welded together by this resistance-welding process. The adjacent end portions of pipes I and 2 having been previously heated by the arc to a high temperature, the resistance of these portions of the pipes will be greater than that of the remaining portions thereof, due to the positive temperature coefficient of resistanceofthe metal. Since the heat. produced by the flow of an. electrical. current. through. a resistanceis proportional. to the product of the square-orthe current. and the resistance through which it is flowing, the higher the resistance the. greater. willbe. the amount of heat produced. 'Ihere.fore;.since. the resistance. of the heated. end portions. of. pipesl: and. 2 is substantially greater than that of the remaining portions thereof, so that, in efiect the total; resistance. of. the pipes is concentrated. in said heatedend portions, the heat produced in the. pipes asa result of the flow of alternating currentirom thesource 3.5-therethrough will also be concentrated in the adjacent endportions (which are now in contact), these ends will berapidly brought up. to welding temperature, and the pipes will be welded together.

As stated above: substantially'no flowingv or drippage: of-the .metal occurs during. the period of arc heating of the-pipes,.whilethetwo ends are separated. Therefore, when the softened ends-of the. two pipes are-pushed. together, there will be substantially no bulging, orfiowing outward of the metal, so that the external diameter'atthe juncture of the two pipes will be substantially the same. as that of the pipes themselves, When .the actual weldis producedv later by the. resistance-welding process, it will be smooth. and uniform. because substantially no flowing of. the metal. is produced by the latter process.

Of course, it is to be understood that this invention is not limited, to the particular details as'described above, as many equivalents will sug- .gestv themselves to those skilled. in the art. For

example, other means. than that shown may be used to. pushtlie. ends of the pipes. together. Other, types of sources than that schematically indicated at. 3|v may be used for heating the ends of the. pipes to Welding. temperature after they. have been pushedtogether. Other types of manually-operated, controls, or even: automatic controls, maybe used to control the arc current source.v and. the. alternating-current heating source. Various. other variations will suggest themselves. It. is. accordingly desired that the appended claims be given.- a broad interpretation commensurate withthe scope of this invention within the art...

What is claimed is:

l. A. system for welding together two members along surfaces. thereof, comprising means for holding said members withv thesaid. surfaces separated. a-source. of. arc current, eans. connecting said source to said members, means for so controlling said source as to cause an arc to strike between said surfaces and as to heat said surfaces to a high temperature below the drip point of said members, means for causing dispersion of said are throughout said surfaces, means for bringing said surfaces into tight engagement, a source of alternating current, and means connecting said last-named source to said members to provide a current flow between said members to heat said surfaces to a welding temperature, said last-named means including means for so controlling said last-named source as to provide said current flow while said surfaces are in engagement.

2. A machine for welding together two members along surfaces thereof, comprising means for holding said members with the said surfaces separated, a source of arc current, means connecting said source to said members, means for so controlling said source as to cause an arc to strike between said surfaces and as to heat said surfaces to a high temperature below the drip point of said members, means for causing dispersion of said are throughout said surfaces,

power-operated means for forcing said surfaces 3. A system for welding together two members along surfaces thereof, comprising means for holding said members with the said surfaces separated, a source of arc current, means connecting said source to said members, means for so controlling said source as to cause an arc to strike between said surfaces and as to heat said surfaces to a high temperature below the drip point of said members, means for causing dispersion of said are throughout said surfaces, means for bringing said surfaces into tight engagement, a source of alternating current, and timing means connecting said last-named source to said members to provide a current flow between said members for a predetermined time to heat said surfaces to a welding temperature, said last-named means including means for so controlling said last-na-med source as to provide said current flow while said surfaces are in engagement.

4. A system for welding together two members along surfaces thereof, comprising means for holding said members with the said surfaces separated, a source of arc current, means connecting said source to said members, means for so controlling said source as to cause an arc to strike between said surfaces and as to heat said surfaces to a high temperature below the drip point of said members, means for causing dispersion of said are throughout said surfaces, means for bringing said surfaces into tight engagement, a separate source of heating current, and means connecting said last-named source to said members to provide a current flow between said members to heat said surfaces to a welding temperature, said last-named means including means for so controlling said last-named source as to provide said current flow while said surfaces are in engagement.

5. A machine for welding together two members along surfaces thereof, comprising means for holding said members with the said surfaces separated, a source of arc current, means connecting said source to said members, means for so controlling said source as to cause an arc to strike between said surfaces and as to heat said surfaces to a high temperature below the drip point of said members, means for causing dispersion of said are throughout said surfaces, power-operated means for forcing said surfaces into tight engagement, means for controlling said power-operated means, a separate source of heating current, and means connecting said lastnamed source to said members to provide a current flow between said members to heat said surfaces to a welding temperature, said last-named means including means for so controlling said last-mentioned source as to provide said current flow while said surfaces are in engagement.

6. A system for welding together two members along surfaces thereof, comprising means for holding said members with the said surfaces separated, a source of arc current, means connecting said source to said members, means for so controlling said source as to cause an arc to strike between said surfaces and as to heat said surfaces to a high temperature below the drip point of said members, means for causing dispersion of said are throughout said surfaces, means for bringing said surfaces into tight engagement, a separate source of heating current, and timing means connecting said last-named source to said members to provide a current flow between said members for a predetermined time to heat said surfaces to a welding temperature, said last-named means including means for so controlling said last-named source as to provide said current flow While said surfaces are in engagement.

JOHN W. DAWSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,654,563 Taylor Jan. 3, 1928 1,780,297 Heineman Nov. 4, 1930 1,857,060 McBerty May 3, 1932 1,916,013 Otto et a1. June 27, 1933 2,231,317 Bernard Feb. 11, 1941 2,286,211 Dawson et a1. June 6, 1942 

